This invention relates to swash-plate type compressors for use in air conditioners for vehicles or the like, and more particularly to improvements in the pistons used in such compressors to provide improved lubrication of sliding portions of the swash plate and the shoes interposed between the pistons and the swash plate.
In a swash-plate type compressor of this kind in general, double-headed pistons are disposed to reciprocatingly move within their cylinder bores in unison with the rotation of the swash plate secured aslant on the drive shaft, for fluid compressing action in cooperation with the suction valves and the discharge valves. Balls and shoes are slidably interposed between the swash plate and the pistons to smoothly convert the rotational motion of the swash plate into corresponding reciprocating motions of the pistons. During the rotation of the swash plate, the sliding portions of the swash plate, shoes, balls and pistons undergo severe friction, requiring permanent supply of lubricating oil. In order to supply lubricating oil to the above sliding portions, the rotating swash plate upwardly splashes lubricating oil stored in an oil reservoir at the bottom of the cylinder block, and the resulting misty oil is supplied to the sliding portions. However, according to this manner, sometimes a required oil supply amount cannot be achieved. Particularly when the swash plate is rotating at a high speed, the shoes slidingly move on the swash plate at a correspondingly high speed, which can result in a shortage of lubricating oil supplied to their sliding surfaces, and sometimes the resulting high frictional heat causes seizure of these parts.